Silicon trench etch

Abstract

An improved method is disclosed for obtaining relatively deep (6 microns) trenches in single crystal silicon wafers. The method comprises exposing the wafer to a plasma formed in a gas mixture comprising Freon 11 (CCl3F), sulphur hexafluoride (SF6) and either helium or argon. The etch takes place at a pressure of 1-3 torr (133-400 Pa) in a narrow gap (6 mm.) planar plasma reactor.

We claim: 
     
       1. A plasma trench etch process comprising the steps of: enclosing a silicon substrate in a plasma reactor having an electrode gap of 3-10 mm;   providing a gas mixture, comprising CCl 3  F and an inert gas wherein the amount of CCl 3  F is less than the amount of inert gas, at a pressure of from 1.0 to 5.0 torr;   applying an RF signal, at a power in excess of 400 watts, to said reactor for forming a plasma within said reactor; and   continuing said process for a period sufficient to etch said silicon substrate.   
     
     
       2. The process as set forth in claim 1 wherein said gas mixture further comprises SF 6  in an amount less than said CCl 3  F. 
     
     
       3. The process as set forth in claim 2 wherein said wafer is enclosed in a reactor having an electrode gap of 6 millimeters. 
     
     
       4. The process as set forth in claim 2 wherein said inert gas comprises helium. 
     
     
       5. The process as set forth in claim 2 wherein said inert gas comprises argon. 
     
     
       6. The process as set forth in claim 1 wherein said inert gas comprises helium.